(1) Field of the Invention
The present invention relates to air-ride suspension systems for vehicles, in particular a suspension system comprising a leveling valve for maintaining a substantially constant vertical distance between the vehicle chassis and its axles in response to loading and unloading of the vehicle and operation of the vehicle over uneven road surfaces, and a pressure accumulator that accumulates increasing fluid pressure from the suspension system air spring, or the air spring and shock absorber, and resupplies the fluid pressure to the air spring, or air spring and shock absorber, when the fluid pressure of the suspension system decreases.
(2) Description of the Related Art
Air-ride suspension systems of the type provided by the present invention commonly comprise a hanger member, a torque beam, an axle seat, and an air spring. The hanger members are connected to and depend from chassis members of the vehicle. The torque beams are pivotally connected to the hanger members at one end, and are connected in some fashion with the axle seat members at their opposite ends. The axle seats support the vehicle axle, and together with the torque beam, they permit the vehicle axle to move vertically relative to the vehicle chassis by pivoting the axle about the pivot connection between the torque beam and the hanger. The air spring is generally positioned between the axle seat and the vehicle chassis, and dampens the forces exerted on the vehicle chassis caused by vertical movement of the axle and axle seat when the vehicle is driven over uneven road surfaces.
Leveling valves are commonly employed in air-ride suspension systems to respond to changes in the vertical distance between the vehicle chassis and the vehicle axle as the vehicle is driven over an uneven road surface. The leveling valves automatically supply or drain pneumatic pressure to and from the air spring of the suspension system respectively, in response to the changes in the vertical distance between the vehicle chassis and the vehicle axle. The leveling valves automatically supply increased pneumatic pressure to the air springs in response to vertical movement of the vehicle axle toward the vehicle chassis to compensate for this movement, and the leveling valves automatically release pneumatic pressure from the air springs in response to vertical movement of the vehicle axle away from the vehicle chassis to compensate for this movement.
A disadvantage of this type of suspension system, and a disadvantage found in many other types of suspension systems employing air springs and shock absorbers, is that the system does not adequately cushion the shock transmitted to the vehicle by the vehicle axle traveling over a large bump or falling into a large hole in the roadway. The large vertical distance that the axle travels and the abruptness of the axle movement cannot be compensated for quick enough by the supply of pressurized pneumatic fluid or release of pneumatic fluid from the air bag, and a large shock results. Moreover, in air-ride suspension systems employing leveling valves, the frequency of the vertical movement of the vehicle axle relative to the vehicle chassis after the axle has passed over a bump or through a hole in the roadway will sometimes be enhanced by the automatic supply and release of pressurized pneumatic fluid to and from the air bag by the leveling valve.
The present invention overcomes the above described disadvantages of prior art air-ride suspension systems by providing a pressure accumulator in fluid communication with the pneumatic fluid of the air spring and the leveling valve. The pressure accumulator serves to dampen the abrupt and substantial increase in pneumatic pressure caused by the vehicle axle passing over a bump or through a hole in the roadway, and also serves to dampen the frequency of vertical movement of the vehicle axle relative to the vehicle chassis after it has passed over a bump or through a hole. The accumulator of the present invention is also adapted to communicate fluidly with a hydraulic shock absorber positioned between a vehicle axle and chassis. The accumulator serves to dampen the abrupt and substantial increase in hydraulic fluid pressure of the shock absorber when the vehicle axle passes over a large bump or through a large hole in the roadway, and it also serves to enhance the ability of the hydraulic shock absorber to dampen the frequency of vertical movement of the vehicle axle relative to the chassis after the axle has passed over a bump or through a hole.
It is therefore an object of the present invention to provide an improved air-ride suspension system for vehicles that employ a pressure accumulator that communicates fluidly with an air spring of the suspension system in one embodiment, and communicates fluidly with an air spring and a hydraulic shock absorber in a second embodiment, where the pressure accumulator serves to further dampen the shock transmitted from a vehicle axle to the vehicle chassis when the vehicle passes over a bump or through a hole in the roadway, and further serves to dampen the frequency of vertical movement of the vehicle axle relative to the vehicle chassis.